Best money I ever spend
Today, unless you're doing heavy processing stuff, CPU speed DOES NOT MATTER. Memory does. I was perfectly happy with the CPU speed of the notebook I had before, the problem of course was memory size.
(I wouldn't buy a 17' notebook, you'll pay the price on back problems)
I can't stand using Windows and the Linux distributions nowadays take much of my time with BS like Gnome 3 and other bloated crap.
So, Mac OS.